POLYMERIC HYDROGEL BASED INSULIN DELIVERY SYSTEM

Transcription

1 POLYMERIC HYDROGEL BASED INSULIN DELIVERY SYSTEM by AMIT KUMAR Centre for Biomedical Engineering Submitted In fulfillment of the requirements of degree of Doctor of Philosophy to the INDIAN INSTITUTE OF TECHNOLOGY, DELHI April, 2007

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3 CERTIFICATE This is to certify that the thesis entitled "Polymeric Hydrogel Based Insulin Delivery System" being submitted by Mr. Amit Kumar to the Indian Institute of Technology, Delhi for the award of the degree of Doctor of Philosophy, in Biomedical Engineering is a record of the original bonafide research work carried out by him. Mr. Amit Kumar has worked under my guidance and supervision and has fulfilled the requirement for the submission of this thesis. The results presented in this thesis are original and has not been submitted in partial or full, to any other university or institute for the award of any degree or diploma. (Dr.Harpal Singh) Professor Centre for Biomedical Engineering Indian Institute of Technology, Delhi Hauz Khas, New Delhi

4 DEDICATED TO 91d9r FAmiLy

5 Acknowledgement I wish to earress my deep sense 0-Fatima to Dr. 'aural Singh, Professor, Centre of Biomedical Engineering (CBME) for his invaluable guidance, encouragement and constructive criticism during this work It would not be possible for me to bring this work in the present form without their support. Working with them has been a rich experience and shall always be a pleasant memory. I am also grateful to faculty members of the CBME for their constant help. I am thankful to Irufian Institute of technology Delhi for providing me necessary facilities and financial aid to carry out the research. I sincerely thank Dr. S.S.Lahiri, Sc.Officer-F, Institute of Npckar Medicine and Meted Sciences (INMAS), DSO for his invaluable discussion during animal and studies. I am indebted to him for his help in providing me laboratory facilities and assistance in Experimental Anima! Facility, INMAS. I am thanicru to the entire research staff and research scholar in his laboratory for constant help. I am deep% grateful- to Dr..91semBhatanagar, Sc-E, Department of Nuclear 91(edicine, Institute of Nyclear Medicine and Aftled Sciences (INMAS), DSO for his guidance and concrete discussion during the Gamma imaging studies. I would like to thanks to all staff and research scholar in his laboratory for their invaluable help.

6 It is also true that this work has been impossible without the cooperation and support of my seniors and friends. In naming them, I am likely to miss many of those who contributed in different ways. I would fike to thankrachna Jain, Chant Tyagi, Lomas Tomar, Geeta Singh, Supriya, and Andendu for helping me throughout the work 914 special' thanks to all Laboratory and Office Staff of Center of Biomedical* Engineering for their timely help. My special thank to my parents my brother.91mcf Tyagi, and all my family members for their love, support and unabated faith in me, which kept me going through this work In the end, I have a special word of praise and appreciation for my wife Prtyanka Tyagi, for her cooperation and encouragement, without whom the completion of this dissertation was impossible. ( mit Ku ar) '31

7 ABSTRACT The application of synthetic polymers to medical problems has increased substantially in the last twenty years. Recently, the study of application of controlled release formulations containing the active substances has grown enormously. In the preparation of these systems, biologically active substances are immobilized in a carrier, generally a polymeric material. These polymeric materials must have the right balance of hydrophilicity/ hydrophobicity and the right charge character and be biocompatible. In the oral delivery of insulin, formidable barriers of digestion and absorption is essential to take in account to improve bioavilibility of insulin by the oral route so that it can attain the appropriate concentration in the body and cause the required hypoglycemic effect. One way to achieve this is to entrap insulin in a polymeric carrier which will protect the insulin from the degradation as long as it stays in the stomach. But upon reaching the small intestine, polymeric carrier becomes active in alkaline medium and releases the biologically active insulin. Many researchers have tried to immobilize or entrap insulin into various ph sensitive polymeric matrices to make the oral insulin delivery possible. A number of different strategies have been explored to improve the oral bioavailability of insulin, like use of penetration enhancers, enteric coatings, protease inhibitors and combinational strategies. The present work is devoted towards the development of a ph sensitive polymeric formulation with high insulin loading efficiency, sustained and efficient delivery of insulin in gastro intestinal tract and development of a polymeric hydrogel based implant for insulin delivery.

8 An oral insulin delivery system based on copolymers of poly(ethylene glycol) dimethacrylate and methacrylic acid was developed and its functional activity was tested in non-obese diabetic rats. Poly(ethylene glycol) dimethacrylates (PEGDMA) were synthesized by the esterification reaction of different molecular weight poly(ethylene glycol) with methacrylic acid (MAA) in presence of acid catalyst. Their degrees of acrylation were found to be in the range of 93 to 95% using proton nuclear magnetic resonance (NMR) spectroscopy. PEG dimethacrylates of molecular weight ranging from 400 to 4000 and methacrylic acid were further copolymerized by suspension polymerization to obtain ph sensitive hydrogel microparticles. FTIR spectra of MAA had characteristic absorption peaks at 1635 cm-1 for carbonyl group and 1697 cm -1 for vinylic groups and a band from 3000 to 3450 cm-1 for OH group of carboxylic group. FTIR spectra of PEGDMA showed peaks at 1635 cm -1 for carbonyl group and 1697 cm -1 for vinylic groups was only observed upto 1000da molecular weight of PEGDMA. PEGDMA with molecular weight 2000da and 4000da showed a broader peak at 1639 cm 1 was observed due to merging of carbonyl and vinylic peaks. While in case of poly(pegdma-maa) microparticles, FTIR spectra irrespective of PEGDMA molecular weight showed intense absorption peak of carbonyl group at 1695 cm-1 due to carboxylic acid groups of PEGDMA and MAA. Surface morphology of various microparticles were analyzed using SEM, which showed the spherical shape at ph 2.5 but microparticles coalesce with each other and appeared like a continuous film at ph 7.4. Surface morphology of various microparticles were also analyzed using AFM, which again confirmed the spherical shape of micropaticles at ph 2.5 and continuous film at ph 7.4. The diameters of poly(pegdma-maa) microparticles increased with

9 the increasing molecular weight of the poly(ethylene glycol) dimethacrylates and was found to be in the range of.4 to 2.7 p.m at ph 7.4 and 5.2 to 25.3 urn at ph 2.5. Insulin was loaded into the hydrogel microparticles by partitioning from concentrated insulin solution. It was found that poly(pegdma4000:maa) microparticles showed the maximum loading efficiency (82%) while the lowest (43%) loading efficiency was observed in case of poly(pegdma400:maa) copolymeric microparticles. In-vitro release studies of insulin-loaded microparticles were performed by simulating the condition of gastrointestinal tract, which showed the minimal insulin leakage (18-25%) at acidic ph (2.5) and significantly higher release at basic ph (7.4). Animal studies were carried out to investigate the abilities of the insulin loaded hydrogel microparticles to influence the blood glucose levels of the diabetic rats. In studies with diabetic rats, the blood glucose level reduced in animals that received the insulin loaded hydrogel microparticles and the effect lasted for 8-10 hrs. It was also observed, two capsules per day of poly(pegdma4000:maa) hydrogel microparticles containing 80 I.U./kg of insulin dose were sufficient to control the blood glucose level of fed diabetic rats between mg/d1. In studies with diabetic rabbits, effect of oral administration of poly(pegdma4000-maa) microparticles loaded with 50 IU/kg insulin dose to over night fasted diabetic rabbits reduced the blood glucose level by 78% within first 4 hrs of the treatment and maintained the same for next 2.5 hrs and then started rising slowly and approached the control value. The effect of insulin-loaded microparticles lasted for at least 10 hrs after the oral administration. Pharmacoscintigraphy studies of technetium- 99m labeled insulin loaded in poly(pegdma4000-maa) microparticles were carried out on diabetic rabbits which showed the sustained release of insulin from the 99m

10 labeled insulin loaded poly(pegdma4000-maa). LDO of the poly(pegdma4000- MAA) microparticles in rats is found to be above 4gm/kg body weight. Repetitive dose toxicity of poly(pegdma4000-maa) microparticles was also carried out in rats and histopathological section of liver, stomach, small intestine and large intestine of rat fed with poly(pegdma4000-maa) microparticles upto six month showed no toxicity. The present work was also devoted towards the development of poly(hema) based hydrogel device containing variable amount of water as porogen for implantable delivery of insulin and evaluation of their physical and insulin release properties. Poly(HEMAco-EGDMA) hydrogel devices were prepared by bulk polymerization in a specially designed cylindrical mold of polypropylene. It was observed in the preliminary studies that hydrogel devices synthesized using AIBN as free radical initiator were transparent, bubble free and having good mechanical properties but difficult to remove from polypropylene mould. While hydrogel devices synthesized using APS/TEMED as free radical initiator was easily removed (within 2-3 minutes) from the PP mold probably due to incomplete polymerization and presence of water (used for initiator solution) which acts as a plasticizer for poly(hema), various amount of EGDMA was taken as crosslinker and different amount of water was also added in the reaction mixture as a pore generating solvent. These hydrogel devices were post cured at 80 C for 2 hrs. FTIR spectrum of poly(hema) shows the absorption bands associated with -C=0 stretching of carboxylic acid group (-COOH) at 1714 cm-1, C-O-C stretching vibration at 1152 cm -1 and appearance of broad band at cm -1 corresponding to OH stretching vibration of poly(hema) hydrogel. Hydrogel devices synthesized using 1% of EGDMA and 7% of water (used to dissolve initiators) showed the highest swelling percentage

11 (50%), while the lowest swelling percentage (8.7%) was observed in hydrogel synthesized with 10% of EGDMA. Surface morphology studies of poly(hema) device was carried out using AFM. Device synthesized using 27% of water showed 800nm pores which were unevenly distributed on the hydrogel surface while device containing 47% of water showed nm pores which were unevenly distributed on the hydrogel surface. The hydrogel device containing 67 % of water showed the pores on the surface with pore size in the range of nm. In-vitro release studies of thallium"' (as a model compound) were carried out using hydrogel devices synthesized using 1% of EGDMA as crosslinker and it was observed that approximately 50% of activity release from the hydrogel device with in first 30 minutes, while the 90% of thallium 201 was released from the device with in next 45 minutes. Poly(HEMA) hydrogel device synthesized using 20% of water showed approximately 18% of insulin release with in first 30 minutes, only 50% of insulin release was observed in 60 minutes. Rest of the insulin takes longer time (165 minutes) to release. Poly(HEMA) hydrogel device synthesized using 20% of water filled with insulin loaded poly(pegdma4000-maa) microparticles showed only 18% of insulin release with in 2days, only 50% of insulin release was observed in 5 days. Hypoglycemic effect of poly(hema) implantable device containing 120 I.U. of insulin loaded in poly(pegdma4000-maa) microparticles showed 60% reduction in blood glucose level within first 24 hrs (Ist day), while highest reduction (70%) in blood glucose level was observed on 3 day after implantation. Animals maintain the 70% reduction in blood glucose level upto 4 days, while 5th day 40% reduction in blood glucose level was observed and then blood glucose level approach the control value by 6th day.

12 Contents Abstract Page No. Chapter I- Introduction and Literature Review Introduction Diabetes Mellitus Types of Diabetes and its Complications Diabetes and Insulin Treatment of Diabetes Mellitus Chemical Agents for Treatment of Diabetes Research in the Direction of Permanent Cure of Type-1 Diabetes Insulin for the Treatment of Diabetes Nasal Delivery of Insulin Transdermal Delivery of Insulin Implantable Delivery of Insulin Limitations of Current Insulin Therapy Oral Delivery of Insulin Physical Barrier in Oral Insulin Delivery Enzymatic Barrier of Oral Insulin Delivery Manufacturing Stability Barrier of Insulin Objective of the Work 28 References 33

13 Chapter II- Synthesis of Monomers and Polymers Introduction Polymeric Hydrogels Classification of Hydrogels Non-Ionic Hydrogels Ionic Hydrogels Polyampholytic hydrogels 46 Part A Synthesis of PEGDMA and its Copolymers 2.2 Experimental Methods Synthesis of PEG dimethacrylate Synthesis of Poly(PEGDMA- MAA) Microparticles Synthesis of poly(sma) Copolymer Results and Discussion Synthesis of PEG dimethacrylate Synthesis of Poly(PEGDMA- MAA) Microparticles Synthesis of SMA Copolymer 51 Part B Synthesis of Poly(2-hydroxyethyl methacrylate) based Hydrogel Device 2.4 Experimental Methods Polymerization of poly(2-hydroxyethyl Methacrylate) Results and Discussion 54

14 2.5.1 Synthesis of Polymeric Hydrogel 54 References 59 Chapter III- Characterization of Monomers and Polymers Introduction 61 Part A Characterizations of PEG dimethacrylates and Their Copolymers 3.2 Experimental Methods Characterization of PEG dimethacrylates Nuclear Magnetic Resonance Spectroscopy Fourier Transform Infrared Spectroscopy Characterization Of Poly(PEGDMA-MAA) Particles Scanning Electron Microscopy Fourier Transform Infrared Spectroscopy Particle Size Analysis Swelling Studies Thermo Gravimetric Analysis Atomic Force Microscopy Characterization of Poly(Styrene-Maleic Anhydride) Physical Properties of SMA Copolymer Fourier Transform Infrared Spectroscopy 'H-NMR Spectroscopy CHN Analysis Thermal Characterization 68

15 Acid Value Determination of SMA Copolymer Results and Discussion Characterization of PEG Dimethacrylates Nuclear Magnetic Resonance Spectroscopy Fourier Transform Infrared Spectroscopy Characterization of Poly(PEGDMA-MAA) Particles Scanning Electron Microscopy Fourier Transform Infrared Spectroscopy Particle Size Analysis Swelling Studies Thermo Gravimetric Analysis Atomic Force Microscopy Characterization of Poly(Styrene-Maleic Anhydride) Physical Properties SMA Copolymer Fourier Transform Infrared Spectroscopy H-NMR Spectroscopy CHN Analysis Thermal Characterization Acid Value Determination 96 Part B Characterization of P(HEMA) Based Hydrogel Devices 3.4 Experimental Fourier Transform Infrared Spectroscopy Thermal Characterization 97

16 3.4.4 Swelling Studies Atomic Force Microscopy Results and Discussion Fourier Transform Infrared Spectroscopy Differential Scanning Calorimetry Thermo Gravimetric Analysis Swelling Studies Atomic Force Microscopy 104 References 110 Chapter-IV Loading and In-Vitro Release Studies Introduction 111 Part A: Loading and In-Vitro Release of Drugs from Poly(PEGDMA-MAA) Microparticles 4.2 Experimental Methods BSA Loading in Copolymeric Particles In Vitro Release Studies of BSA Preparation and Loading of 8-Hydroxyquinoline Hydrochloride in Copolymeric Microparticles In Vitro Release Studies of 8-HQ-Hcl Insulin Loading of Microparticles In-Vitro Insulin Release Studies 119

17 SMA Coating of Insulin Loaded Microparticles In Vitro Insulin Release from SMA Coated Microparticles Results and Discussion BSA Loading in Copolymeric Particles In Vitro Release Studies of BSA Preparation and Loading of 8-Hydroxyquinoline Hydrochloride in Copolymeric Microparticles In Vitro Release Studies of 8-HQ-Hcl Insulin Loading of Microparticles In Vitro Insulin Release In Vitro Insulin Release from SMA Copolymer Coated Insulin Loaded Microparticles 138 Part B: In-Vitro Release Of Studies From Poly(HEMA) Based Implantable Devices 4.4 Experimental Methods In-Vitro Release of Thallium201 from poly(hema) Hydrogel Device Loading and In-Vitro Release of Insulin from poly(hema) Hydrogel Device Loading and In-Vitro Release of Insulin Loaded Microparticles from Hydrogel Device Antimicrobial Studies Results and Discussion 142

18 4.5.1 In-Vitro Release of Thallium20' from Hydrogel Device Loading and In-Vitro Release of Insulin from Hydrogel Device Loading and In-Vitro Release of Insulin Loaded Microparticles from Hydrogel Device Antimicrobial Studies 144 References 147 Chapter-V In-Vivo Insulin Release and Toxicity Studies Introduction 149 Part A : In-Vivo Insulin Release from Poly(PEGDMA-MAA) Microparticles and their Toxicity 5.2 Experimental Methods In-Vivo Insulin Release Studies on Rats Effect of Oral Microparticles on Fasted-Diabetic Rats Effect of Oral Microparticles Coated with SMA Copolymer on Fasted-Diabetic Rats Effect of Oral Microparticles on Fed-Diabetic Rats In-Vivo Insulin Release Studies on Rabbits Effect of Oral Microparticles on Fasted-Diabetic Rabbits Effect of Oral Microparticles on Fed-Diabetic Rabbits Pharmacoscintigraphy for Evaluation of Microparticles 157

19 Radiolabel ling of insulin by 99m Tc-pertechnetate as Radionuclide 'Tc-insulin Loading of Poly(PEGDMA MAA) Microparticles Gamma Camera Imaging of 99mtc-Insulin Loaded Microparticles on Diabetic Rabbits Toxicity Studies Conventional Acute Toxicity (LD50) Test Repetitive Dose Toxicity Histopathological Testing of Poly(PEGDMA4000 -MAA) Microparticles Preparation of Tissue Samples for Microtomy Microtomy and Staining of Tissue Samples Results and Discussion Animal Studies on Rats Effect of Oral Microparticles on Fasted-Diabetic Rats Effect of SMA Coated Insulin Loaded Microparticles on Fasted-Diabetic Rats Effect of Oral Microparticles on Fed Diabetic Rats Animal Studies on Rabbits Effect of Oral Microparticles on Fasted-Diabetic Rabbits Pharmacoscintigraphy for Evaluation of Microparticles Selection of 99mtc-Pertechnetate as Radionuclide for

20 Radiolabeling 'Tc-Insulin Loading of Poly(PEGDMA4000 -MAA) Microparticles Gamma Camera Imaging of 99nitc-Insulin Loaded Microparticles on Diabetic Rabbits Toxicity Studies Conventional Acute Toxicity (LD50) Test Repetitive Dose Toxicity Histopathological Testing of Poly(PEGDMA4000-MAA) Microparticles 180 Part B : In-Vivo Insulin Release Of Insulin From Poly(HEMA) Based Implantable Device 5.4 Experimental In-Vivo Insulin Release Studies of Poly(HEMA) Implantable Device on Rabbits In-Vivo Insulin Release Studies from Insulin Loaded Poly(PEGDMA4000-MAA) Microparticles Loaded in Poly(HEMA) Implantable Device In-Vivo Insulin Release Studies from Poly(HEMA) Implantable Device Results and Discussion In-Vivo Insulin Release Studies of Poly(HEMA)

21 Implantable Device on Rabbits In-Vivo Insulin Release Studies from Insulin Loaded Poly(PEGDMA4000-MAA) Microparticles Loaded in Poly(HEMA) Implantable Device In-Vivo Insulin Release Studies from Poly(HEMA) Implantable Device 190 References 191 Chapter-V Summary and Scope of Future Work Summary Scope of Future Work 196